Final answer:
Physical inactivity can cause muscle atrophy, arthrofibrosis, and bone disorders such as osteoporosis. Aging can lead to inevitable sarcopenia, while diseases like cancer and muscular dystrophies further contribute to muscle and bone degradation. Regular exercise can delay age-related atrophy but cannot completely prevent it.
Step-by-step explanation:
Physical inactivity may cause muscle atrophy, arthrofibrosis, cartilaginous degeneration, and bone atrophy. Conditions like cancer and AIDS can lead to a body wasting syndrome known as cachexia, which induces skeletal muscle atrophy. In addition to disease, aging also leads to sarcopenia, a gradual decrease in skeletal muscle mass, with an unclear cause possibly related to decreased growth factor sensitivity.
Moreover, the lack of exercise significantly contributes to muscle atrophy. It affects cellular changes and results in a weakened muscle structure. For instance, astronauts experiencing prolonged periods of weightlessness or individuals on extended bed rest tend to show signs of muscle weakening and atrophy. In parallel, bone disorders such as osteoporosis also involve the reduction of bone tissue per unit volume, resulting in skeletal weakness and a higher risk of fractures. Certain lifestyle factors like poor diet, smoking, alcohol consumption, and lack of exercise play crucial roles in promoting bone resorption.
Muscular dystrophies, including Duchenne muscular dystrophy (DMD), are characterized by progressive skeletal muscle weakening due to the absence of proteins like dystrophin. The absence of dystrophin leads to cellular damage and a progressive loss of muscle mass. This emphasizes the importance of muscle maintenance, either through exercise to delay sarcopenia and disuse atrophy or through careful management of diseases that can accelerate muscle and bone degeneration.